Multiple fuel burner and space heater



R. H- HUNTER ET AL 2,876,763

MULTIPLE FUEL BURNER AND SPACE HEATER Filed June 15. 1955 March 10, 19594 Sheets-Sheet 1 ATTOQNEYS March 1 1959 R. H- HUNTER ETAL I 2,876,763'

MULTIPLE FUEL BURNER AND SPACE HEATER Filed June 15, 1955 4 Sheets-Sheet2 50 55' FLE-E. EE-E INVENTORS POBEE'T Hulk/TEE AND BY Pa /4 5. DAMON{JTTOQNB S March 10, 1959 R, HUNTER IEI'AL 2,876,763

MULTIPLE FUEL BURNER AND SPACE HEATER Filed June 15, 1955 4 Sheets-Sheet3 INVENTORS P019527 H HUNTEE M0 BY Paw 5. DAMo/v Mm Mr s aw.

ATTOENEYfi "Mamh 1959 R. H. I-VIUNTER ET AL 2,876,763

MULTIPLE FUEL BURNER AND SPACE HEATER Filed June 15, 1955 4 Sheets-Sheet4 Q filil/ENTOR. 0 55/27 UNTEE AND FIE A By QALPH 5. DAMON Bow-011%, 5W

#0144150; MW ATTOEA/EYi United States Patent MULTIPLE FUEL BURNER ANDSPACE HEATER Robert H. Hunter, Gates Mills, and Ralph 5. Damon,Cleveland, Ohio; said Damonassignor to said Hunter Application June 15,1955, Serial No. 515,686

8 Claims. (Cl. 126-110) This invention relates to atomizing liquid fuelburners, more particularly to such burners designed for use with fuelsof different viscosities. It has been recognized that liquid hydrocarbonfuels can be efliciently burned by spraying them into combustionsupporting atmospheres. Various arrangements have been devised toimprove the characteristics of the spray, to provide turbulence andspecialized rotary and spiral movements of the air or ent .invention toprovide a fuel burning method and a metal fuel burner which are adaptedto the use of liquid fuels of different viscosities, weights and values.In accordance with this aspect of the invention the fuel is projectedfrom a nozzle under pressure in an expanding spray pattern into one endof a helically rotating air mass, the spray entering the air mass in aplane normal to the spray axis and spaced axially from the spray nozzle.The cross sectional area of the spray in the plane at which it entersthe air mass represents only a small fraction of the cross sectionalarea of the air mass, so that the spray is completely surrounded by, andits outer portions entrained in, the rotating air to maintain the liquidfuel particles in suspension during burning. As a refinement of theprocess the rotating, helically advancing air mass into which the fuelspray is projected constitutes the secondary air for combustion, theprimary air being mixed, as in asuitable nozzle, with the liquid fuel ator prior to the instant the fuel is sprayed into the rotating airmass.As a further refine spaced axially along the length of the rotating massand distributed about its outer periphery or circumference. In aspecialized version concerned with this aspect of the invention thecombustion chamber is defined by inner flame shield and outer shroudcombustion tubes of circular section disposed in coaxial relation andseparated by an annular air supply chamber. The inner flame tube isformed with a plurality of distributed openings through which airintroduced under pressure into the annular chamber is admitted,preferably tangentially, into the interior of the flame tube, thetangentially entering air effecting the desired rotation of the air massinside the flame tube, such a structural arrangement being a furtherobject of the invention.

Another object is to provide a burner of the character mentioned inwhich the fuel projecting nozzle is maintained during operation at atemperature sufiiciently low to eliminate objectionable carbonizationwhile the sprayed fuel is prevented from contacting relatively lowtemperature components of the structure until after combustion iscomplete, elimination of objectionable carbon deposits that. wouldinterfere with the continued eflicient functioning of the burner beingthus obtained. This objective is achieved by the projection of the fuelin an expanding spray pattern through a matching opening in a controlplate which delineates the hot burning zone from a relatively lowtemperature non-burning zone or chamber spacing the nozzle from theburning zone. This aspect of the invention contemplates an elongatedcombustion tube or tubes disposed in coaxial relation to the projectionaxis of the nozzle. The aperture control plate is disposed transverselyacross the interior of the tube or tubes to divide such interior intothe low temperature normalizing chamber adjacent the nozzle and the hightemperature flame chamber remote from the nozzle, the flame chamberpreferably being much longer and larger than the normalizing chamber. Inthe arrangement mentioned, wherein an inner flame tube and an outershroud tube are disposed in coaxial relation in the provision of anannular air chamber, secondary air is introduced tangentially into oneend of such annular air chamber and,

in circulating between the combustion tubes, cools the latter whilebeing heated. The air and fuel receiving ends of the combustion tubesare closed by a metal plate to which they are rigidly attached, thisplate desirably constituting the apertured control plate through whichthe fuel spray is projected. A hollow member,

also of metal, is secured against the outside of the closure plate andcarries the fuel projecting nozzle. The metal nozzle body'is rigidlysecured to the hollow mountingmember in a wall of the latter which isspaced from 'the apertured control plate so that the spray from thenozzle is projected across the chamber of the mounting member beforepassing through the aperture of the control plate into the combustionchamber of the flame tube. The cooling effect obtained by introductionof the secondary air spirally into the receiving end of the combustiontube or tubes is thus effective by reason of the heat conductingcharacteristics of the rigidly connected together metal components inkeeping the nozzle body at a sufliciently low temperature to preventcarbonization of the fuel in or on the nozzle. As a refinement of thisaspect of the invention the nozzle body and the related components aremade of heavy sectioned brass or similar metal of high heatconductivity, and primary air is led through such heavy sectionedcomponents and into a mixing chamber in the nozzle to provide localizedcooling ofthe nozzle structure. As a further refinement of the nozzlearrangement there is provided a protective cap or-shield, whichdesirably takes the form of a hollow cup disposed in embracing relationover the nozzle. The cup is mounted in heat conducting air receivingrelation to "the'nozzle supporting member and is formed with an openingthrough which the received air mixed with the expanding spray isprojected, these being further objects of the invention.

Other objects and advantages relate to certain novel features ofconstruction and combinations and arrangements of parts devised toachieve simplicity in construction, service and repair and economy inmanufacture and operation. These and the preceding objects andadvantages are apparent in the following detailed description of theinvention made in connection with the accompanying drawings forming apart of the specification.

In the drawings:

Figure 1 is a side elevational view partly in section with parts brokenaway and removed and partly diagrammatic showing a space heaterincorporating the burner out the top opening 5.

heat exchanger and control principles of the present invention;

Fig. 2 is an elevationaldetail of the rear end of the nozzle mountingmember showing the nozzle and the ignition electrodes, this-'viewbeingenlarged with respect to Fig. 1;

Fig. '3 is a fragmentary side'elevational detail partly in section andwith parts broken away and removed showing the nozzzle mounting memberand related parts of part broken away, taken transversely through'theheater of Fig. l and enlarged with respect to that figure.

The space heater shown in the drawings and representing the best knownmode of practicing the invention comprises 'a generally rectangularcasing having top 1, bottom 2, end walls3 and 4, and side walls, one ofwhich -is removed in Fig. 1 and the other of which is behind theillustrated components and is parallel to the plane of the drawing. Thecasing is formed with sheet metal bolted, welded or riveted together andprovided with suitable openings through which the fuel and electricalconduits and conductors are admitted. One or bothof the side walls areformed with louvers or grills'to admit atmospheric-air into the casingfor circulation through the heatexchanger and to supply combustionairfor the burner. -An openings in the casingtop 1is covered by ascreen6, this opening constituting the exit through which-heated air isdischarged after'passing through-the heat'exchanger. The burner and-heatexchanger are suspended;as-a-unitfrom thfecasing top -1 and -occupy-theupper-half'of the casing. The heatexchanger is'enclosed between spacedparallel side partition panels 7 and 8 of sheet metal flanged alongtheir upper'edges for securement as by screws 9 against the underside ofthe casing top panel 1 along the margins of the opening 5. A bottompanel 10, also sheet metal, has parallel edge flanges 11 and 12 whichlap the bottom edges of the Side panels 7 and 8 and are welded to thelatter in the provision of a shelf on which the heat exchanger andburner are supported.

The-heat exchanger comprises a pair of hollow sheet metal headers 15 and16, each of generally rectangular configuration and constructed of heat-resistant sheet metal, such'as stainless steel, suitably formed andwelded together. These'headers have approximately the-same dimensionsand are of such size that they 'have'easy-slid- --ing fits onto thesupporting shelf -and --between-the spacedsidespanels 7 and 8. eachspaced inwardly from the side walls of the'heater casing to permit thecirculation of air between the. panels The panels 7 and 8 are '7 and 8and the casing walls which they confront, thereby preventing excessiveand localized heating of the casing walls. 7 p

By making the headers and 16 so that they closely changer so that'airforced into the bottom'of the heat exchanger is confined to flowupwardlytherethrough and It is apparent, of course, that tight sealingbetween the headers and the walls and bottom of the'internal shell orcasing of the heat exchanger is unnecessary since-air which escapes intothe interior of the main casing-is merely recirculating through the heatexchanger.

The header 15 thus includes inner and outer walls 17 and 18 disposed inspacedparallel relation to one another and connected by top andbottomwalls 19 and 20. This ---into the header walls.

4 header also includes side walls one of which, shown at 21 (Fig. 5), isdisposed against the inside of the panel 7 and the other of whichisdisposed against the inside of the panel 8. Extending through chamber22 of the header 15 is a cylindrical sleeve 23 the ends of which arereceived in flanged openings in the header walls 17 and 18 by circularwelded joints 24'which seal the sleeve ends Thisslecve receives andaccommodates outer combustion tube or shroud 25 of the burner in asliding fit.

The'header-16 comprises inner and outer walls 27and 28 corresponding-tothe heat resistant stainless steel walls 17 and'1 8 of the header 15.Top and bottom walls 29 and 30 correspond -to the walls 19 and 20previously described and the header 16 has side walls corresponding tothe side walls of the header 15, one side wall of the header 16 beingindicated at 31.

The end of the combustion tube or shroud 25 projects through a flangedcircular opening'inthe inner wall 27 of the header 16 and iswelded tothe wall flange in the provision of a circularseal 33 that secures thetube to the header wall. As will appear, hot gases projected intochamber 32 of the'head'er 16 through the discharge end of the combustiontube "25 are circulated between the headers arid ultimately discharge toatmosphere through a suitable exhaust tube or conduit (notshown)connected tubes 35 which areof stainless steel or other heatresistant ine'tal.

These tubes are made from cylindrical tube'blanks of uniform circularcross section. At spaced points along its length each tube blank ispartially collapsed orcrushed by the application of localized radial-forces actingtowardoneanother on a common diameter 50 as to impart tothe tube an ovoid cross section (Fig.

5). The deforming of the tubes 35 may be accomplished,-for example, in apress 'or stamping machine provided with opposed jaws representeddiagrammatically at-36'and 37 (Figs. 1 and 5). The jaws have elongatednarrow working faces or edges 38 arranged in parallel relation andmovable toward and away from one another. As the jaws are brought towardone another under power in a'working-stroke'the walls of the cylindricaltube blank are forced toward one another forming wide angled generallyV-shapedcreases 39 which confront and are parallel to one another.

In making successive deformations along the length of the tube blank thelatter is rotated approximately -between the crushing operations so thatthe long axis of -each-of the ovoid-sections is angularly disposedrelative {to-the co'rrespondingaxes of the adjacent ovoid sections.

The tube blanks of which the exchanger tubes 35 are formed areundisturbed at their endsso that such'ends -remain ofcircular sectionandare inserted'into'the inner walls '17 and 27 of the headers throughcircular flanged openings, each tube end being welded to the embracingfianges'in the-openings in the provision of circularseals cation withthe outlet tube or nipple 34. The gases or fluid heatingmedium enteringthe lower portion of the header 16"are'thus constrained by the diagonalpartition or baffle '42 fto flow through the lower tubes 35 to theheader 15. Inthe chamber 22 of the header 15 the 'hot' gasesreceivedthroughthe lower tubes flow upwardly about the sleeve 23 andinto the upper portion of the header chamber- 22. The gases from the iupper portion ofthechamber22 return to-the"header 16 throughthe uppertubes 35 of the heat exchanger entering the. chamber 32 above the bafllepartition 42.

Circulation of atmospheri: air through the heat exchanger is induced bya blower, or fan 44 carried on a shaft 45 journaled in bearings whichsupport the fan in a sheet metal scroll 46. The outlet of the fanscroll, indicated at 47, is of rectangular shape and registers with anopening 48 in the bottom panel or shelf of the heat exchanger. Anintegral flange 49 on the fan scroll outlet is disposed flatwise againstthe underside of the bottom panel 10, being secured to the latter as byscrews 50 which support the entire fan assembly. An electric motor 52mounted in the casing drives the fan 44 by belt 53 trained aroundpulleys on the motor shaft and the shaft 45 of the fan assembly. Themotor 52 is controlled conventionally to operate the fan to force airinto the chamber defined by the heat exchanger panels 7, 8 and 10 andthe headers and 16 in response to heat demand registered by thermostator other suitable indicator. If desired, the motor circuit may be connected in parallel with the burner control circuit, to be laterdescribed, so that the burner and fan are started and stoppedsimultaneously. Alternatively the fan motor may be controlled separatelyfrom the burner to provide a preliminary period of burner operationduring which the heat exchanger is brought up to temperature andsubsequently the fan is started and to provide, if desired, a terminalperiod during which the fan is continued in operation after the burneris shut down so that movement of air through the heat exchanger iscontinued for sufficient time after the burner stops to cool the heatexchanger tubes and headers and thereby reduce stack losses in theover-all operation of the space heater. It is apparent, of course, thatsince the fan scroll 46 is located within the casing walls, the lattermust be formed with openings through which the air to be forced throughthe heat exchanger is first drawn into the interior of the casing.

The combustion chamber of the present burner is defined by thecylindrical outer tube and by a shorter inner flame shield tube 55. Thisinner tube is of cylindrical shape and is mounted within and coaxial tothe outer tube 25, the two tubes being separated 'by an annular chamber54 into the left end of which, as viewed in Fig. l, secondary air isintroduced tangentially through a pipe 59. Both the inner flame tube 55and the outer tube 25, which constitutes a shroud for the inner tube,are constructed of heat resistant sheet metal such as stainless steel inorder to withstand the high temperatures to which they are subject. Theinner flame tube 55 extends outwardly an appreciable distance beyond theouter Wall 18 of the manifold 15 and it is desirable that the annularair chamber 54 be coextensive in length with the inner flame tube. Toachievesuch an arrangement it is feasible, of course, to extendthe'outer tube 25 to the left end of the inner tube 55. To facilitatemanu- -facture and assembly, however, it is contemplated to utilize asupplemental cylindrical tube 56 which extends as a continuation of thetube 25, the two tubes being held together in end to end relation by ajoint comprising outwardly projecting radial end flanges 57 and 58secured as by bolts or screws (not shown).

Across the outer end of the supplemental tube 56 is secured a closureand control plate 60 to the inside of which the inner flame tube 55 issecured as by means of radially inwardly directed flange 61. The plate60 is formed with a central circular opening 62 through which the fuelspray is projected from a nozzle assembly, indicated generally at 63.The nozzle and control plate opening 62 are centered on the axis of theburning tubes 25, 55 so that the fuel spray is centered in the opening62 and is projected into the center of the air mass within thecombustion tube.

A nozzle structure or assembly 63 is carried by a circular plate 64disposed across the end of a hollow cylinthe parts snugly together.

drically shaped mounting member 65 which issecured against the outerface of the control plate and constitutes a continuation of thecombustion tube component. The parts are conveniently located and heldin place as by screws68 (Fig. 3) which extend through aligned holes inthe plate 64, the body of the hollow mounting member 65, and the endclosure and control plate 60, the inner ends of the screws beingthreaded into the circular flange 61 of the fiame tube 55 so as to drawThe cross sectional area of chamber 66 in the mounting member is largerthan that of the circular control opening 62 so that, in effect, thecontrol plate 60 constitutes a partition dividing the interior of thecombustion tube structure (which comprises the inner flame tube 55, theouter shroud 25, the supplemental tube 56, and the circular sectionedmounting member 65) into the outer or normalizing chamber 66 ofrelatively short axial length and the inner combustion chamber locatedwithin the inner and outer tubes 55 and 25.

The nozzle structure 63 comprises a body 70 which may take the form of aturning of brass or similar machinable metal of high heat conductivity.It is formed with a central axial fuel passage 71 and a number ofprimary air passages 72. The central fuel passage 71 is reduced adjacentthe outlet orifice of the nozzle in the provision of a tapered orfrustoconical valve seat. The air passages 72 open into an annularchamber 73 which is provided by a hollow cap 74 fitted over the end ofthe nozzle body and held by a shouldered sleeve 75 threaded onto theoutside of the body. The cap 74 is formed with a central orifice 76through which air is discharged from the nozzle tip chamber 73. An axialprojection 77 on the nozzle body 70 extends into the opening of theorifice 76 with a surrounding clearance to provide the desired annularair escape passage of the nozzle orifice 76. The projection 77 is formedwith the aforementioned small diameter extension of the axial fuelpassage 70 through which the liquidfuel under pressure is projected intothe center of the air stream issuing through the circular nozzle 76.

The nozzle body 70 is formed with an externally threaded extension ofsmall diameter which is screwed into one end of an internally threadedtransverse passage 79 of a mounting block 80. The fuel passage 71 iscontinuous through the threaded extension of the nozzle body and opensinto the chamber provided by the threaded passage 79 in the block 80. Anelongated stem 81 of a needle valve structure extends axially throughthe threaded passage 79 and the fuel passage 71, this stem having atapered end'82 which is movable toward and away from the frustoconicalvalve seat in the fuel passage in regulating the rateof fuel flow or toseal the passage. The stem 81 has a portion intermediate its endsthreaded through an axial threaded passage in a fitting 83 screwed intoand constituting a closure for the threaded passage 79 in the mountingblock 80. Rotating the valve stem 81 as by thumb wheel 84 on its outerend shifts the stem axially in adjusting the valve. Suitable packing inan annular chamber provided in the outer end of the fitting 83 insurrounding relation to the stem 81 is held in place by a cap 85threaded onto the fitting 83 to provide a fiuid tight seal around thevalve stem. Fuel is supplied to the nozzle assembly through a tubularconduit 86 the end of which is connected as by threaded fitting 87 to achamber 88 in one end of the nozzle mounting block 80. The nozzle blockchamber 88 receiving fuel under pressure from the conduit 86communicates with the transverse threaded passage 79 through alongitudinal drill hole so that the fuel flows freely into the fuelpassage 71 and, when the needle valve is open, into the reduced diameternozzle passage from which the fuel is projected through the orifice andmixed with the air in an expanding conical spray pattern.

"nozzle orifice. and related nozzle components are contemplated to pro-Air is' supplied to the nozzle steamin block80 through a co'uduit ortube9 threaded into a socket in the end of-the bl'oek 80opposite the socketwhich receives the threaded fuel'tube fitting '87. From chamber 91 inthe right-hand end oftlie nozzle block 80, as viewed in Fig. 4,

the primary air 'un'der'pressure enters an annular passage '92 whichsurrounds the previously mentioned threaded 92 in the attachingblock'sll to receive air from "the latter. The oblique air passages 72communicate with "the channel 95 to receive air therefrom which isconducted thence into the nozzle tip chamber 73, as previouslymentioned. The base end of the nozzle body 70 and the face of themounting block boss 93 are machined and finished with matching faceswhich come together in the provision of a fluid tight-seal whicheliminates the loss -of.pressuriz'ed air from the annular channels 92and 95.

In mounting the nozzle assembly 63 on the circular supporting plate 64 acentral circular opening 96 formed in the plate is received over thecircular boss 93 of the mounting block and the parts are brazed togetherbefore the nozzle body 70 is screwed into the mounting block 80. Thenozzle body and other components of the nozzle assembly are thenassembled with the mounting block'80. Received over the nozzle body andalso over the nozzle end member 74 and threaded collar 75 is aprotective cap or shield 97 which is cupshaped and has relatively thickcylindrical walls and a relatively thin end wall 98. The end of the cup97 is abutted against the supportingiplate 64, being received through acircular opening 99 in a web or partition 100 adjacent the end of themounting member 65. The partition 100 is separated from the end plate64, which carries the nozzle assembly by annular insulating air space101 which surrounds the nozzle assembly. In addition to being abuttedstrongly against themounting plate 64 and being fixedly body 70 in theprovisionof good heat conducting relationship between the protective capand the mounting plate '64, iioz'zle mounting body 80 and the mountingmember 65. The end wall 98 of the protective cap 97 is separated fromthe endelement 74 ofthe nozzle as- "senibly by a clearance space orchamber 104 which serves as an insulator and prevents the absorption ofradiant heat energy by the nozzle tipmember 74 directly from "the'fla'r'neburnin'g in the tube 55. A central opening lilo in'the'thinendwall 98 of the'protective cap 97 is axially 'alig'nedwith' and is'suiiicien'tly larger than the discharge orifice 76 to clear the conicalspray issuing from the Various designs of the nozzle orifice 76 vide asuitable expanding spray pattern. In one ar- 'ra'nge'in'e'nt 'which' issatisfactory for the relationships il- 'lu'stratedfthe liquid fuel andprimaryair issue from the nozzle orifice in a conical spray patternhaving an include angle of approximately l30. The diagrammaticrepl'res'entation of the spray shown in Fig. ldoes not represent the"true spray angle but is merely shown to indicate the "direction andlocation of the expandingspray. The arr'anger'nent of the 'parts issuch, with reference to the epeningms in jtheprotective cap '97 and theopening 62 "in 'tlieebnt'rolplateftifi, that the expanding conical sprayis rojected frohtthenozz'lebrifice 76 across the norobservedthat theopening 106 in the circular attaching flange 61 of'the flame-tube isappreciably larger than thecontrol plate opening 62.

Ignition is effected by a hi h tension electricalspark produced across agap between the ends of electrodes 10 108 and 109 mounted in insulators110. The insulators are held in externally threaded metal tubularfittings 111 secured in-the circular supportplate 64. Openings 112 are,provided in the partition 10% in alignment with the tubular fittings 111to accommodate the electrodes and insulators. As shown in Fig. 1 theouter ends of the electrodes are connected as by wires 114 and 115 tosecondary of a transformer 116. The primary of the transformer isconnected to the electrical circuit which energizes the burner so thatwhenever the burner is energized to supply heat the transformer islikewise energized to maintain continuous ignition spark across theelectrodes 108 and 109.

One of the refinements of the primary air supply system is concernedwith the by-passing of a portion of the primary air around the chamber73 at the end of the nozzle body and through the cap chamber 104. Thissupplemental air supply is obtained through a hole 103 drilled throughthe nozzle mounting blockand the circular mounting plate 64 from theprimary air chamber 91 in the nozzle block to the annular air space orchamber 101 located between the partition and the circular nozzlemounting plate 64. A number of radial holes 107 are drilled through thecylindrical side walls of the cap 97 at the base end of the latter so asto place the interior of the cap in communication with-the chamber 101.The supplemental air fed into the chamber 101 through the drilledpassage 103 thus flows into the base of the cap 97 ata plurality ofpoints and thence flows axially inside the cap to the chamber 104located between the internal nozzle structure and the end wall 98 of theprotective cap. This supplemental air flows across the flats of the hexportion 102 of the nozzle body 70 and through an annular clearance spacebetween the shouldered sleeve 75 and the internal surface of the cap 97.The supplemental air cools both the cap 97, which is subjected to theradiant heat energy from the flame, and the internal nozzle structure toprevent these parts becoming heated to temperatures which causecarbonizationof the fuel. In flowing radially across the face of the cap74 of the internal nozzle structure the supplemental air moves radiallyinto the air stream issuing through the nozzle orifice 76. Thecommingled primary air and the supplemental air together constitute thevehicle which carries the fuelreleased through the central fuel orifice.Some of the 'air forcedinto the chamber- 101 escapes --into thenormalizing chamber 66 through the openings 112 for the electrodes,thereby keeping such openings clear of soot and other objectionabledeposits.

Both primary air and secondary air are supplied to the burner by acentrifugal blower suitably supported within the casing of the heaterand driven by an electrical motor (not shown) connected to-shaft 121 ofthe blower. The motor for the blower 120 is connected in parallel withthe transformer 116 so that the blower, like the transformer, isenergized whenever the thermostat or other control or indicator devicedemands heat ed tangentially into the rad tlly narrow annular chamber 54which separates the inner flame tube 55 and the outer shroud tube 25.The entering secondary air is thus induced to a helical flow in theannular chamber and at points spaced along its helical path theadvancing secondary air is released, preferably tangentially, into theinterior of the flame tube 55 through apertures distributed bothlongitudinally along and circumferentially about such flame tube. Thesesecondary air inlet apertures may be arranged in various patterns,preferably so that the ratio of inlet aperture area to flame tube areaincreases progressively from left to right in Fig. 1, this being thegeneral direction of flow of the air in the annular chamber 54 and also,of the helically rotated air mass within the flame tube. In thearrangement shown the apertures are distributed in accordance with ageometric pattern. The apertures are arranged in circumferentiallyextending rows, the rows being located in parallel planes spaced alongthe length of the inner combustion or flame tube. To obtain the desiredincreasing ratio of aperture opening area to tube area thecircumferential rows may be spaced progressively closer together towardthe outlet end of the flame tube or, as shown, the aperture rows may beuniformly spaced with the apertures increasing in diameter or area fromleft to right, this being the direction of air flow in both the annularair chamber which surrounds the flame tube and the interior combustionchamber. For example, in a burner having an outer combustion tube 25 ofabout 4 inch inside diameter and a tributed openings 125 are inchdiameter and are located in a transverse plane parallel to and spacedapproximately 2 inches from the circular opening 62 in the control orpartition plate 60 which separates the combustion chamber from thenormalizing chamber 66 of the composite combustion tube structure.Apertures 126 of the next succeeding row are distributed about the flametube in a plane spaced in the direction of air and flame travelapproximately 1 /2 inches from the plane of the apertures 125, theapertures 126 being approximately inch diameter. Aperturer 127comprising the third row are in a transverse plane spaced approximately1 /2 inches from the plane of the apertures 126 and are inch in diameteror slightly larger but less than inch in diameter. Apertures 128 of thefourth row and 129 of the fifth row are in transverse planes each spacedapproximately 1% inches from the plane of the preceding row of aperturesand are inch in diameter or larger. The apertures 128 and 129 may be ofthe same diameter or, preferably, the apertures 129 are slightly largerthan the apertures 128. Each group or circumferential row consists ofeight apertures uniformly distributed, the apertures of each row beingoffset circumferentially with respect to the apertures of adjacent rows.

The secondary air supply tube 59 projects the air into the annularchamber 54 through an opening 130 which is located intermediate theplane of the control or partition plate 60 and the plane of the firstgroup of apertures 125. Thus is insured circumferential flow of thesecondary air in the chamber 54 so that such air approaches the plane ofthe apertures 125 as well as the succeeding apertures in a helical flowpattern. In this manner the secondary air is induced to enter thecombustion chamber within the flame tube 55 in a multiplicity oftangential jets which cause the mass of air in the combustion chamber torotate about the axis of the combustion tube structure and to advancehelically as a column from left to right as viewed in Fig. 1. When theexpanding fuel spray is projected axially into the center of thereceiving end of the rotating air mass and ignited, the resulting flameand combustion products are likewise induced to rotate by reason oftheir entrainment in the secodnary air mass. Augmentation of thesecondary air mass by tangentially directed airjets distributed alongits length and about its circumference maintains the fuel particles insuspension while they are being raised to ignition temperature andburned. The depositing out of fuel and carbon on the walls of thecombustion chamber is thus minimized with resulting improvement inefliciency and elimination of frequent cleaning and servicing of thecombustion tube, structure. This is a specially desired feature inconnection with the burning of fuel oil of the type used in domestic oilburners or aircraft jet engine oil which are liquid fuels of relativelyhigh viscosity compared to gasoline. By reason of the heating of thecombustion tubes from the internal flame, the heat being conducted alongthe tubes toward the supplemental outer tube 56 and the tubular mountingmember 65, these components of the combustion tube structure at thenozzle end become hot and preheat the secondary air which flowscircumferentially about that portion of the annular chamber 54 insidethe supplemental outer tube 56 before being projected into thecombustion chamber through the apertures 125. Thus, the enteringsecondary air cools the end of the combustion tube structure whichcarries the nozzle assembly 63 so that objectionable overheating of thenozzle is avoided.

Adjacent the outlet end of the flame tube 55 the latter is embraced by acentering ring 123 which is in circumferential contact With the insidewalls of the outer combustion or shroud tube 25. This ring, in additionto supporting the flame tube 55 in coaxial relation to the shroud tube25 so as to maintain concentricity and uniformity in the radialdimension of the annular air chamber 54 constitutes a closure for theend of such annular air chamber. By thus sealing off the end of theannular air chamber that surrounds the flame tube the secondary airforced tangentially into one end of the annular air chamber by theblower feeding through the conduit 125 and the tangential inlet tube 57is forced to flow into the combustion chamber within the flame tube 55through the openings distributed along and about the flame tube. Toinsure tangential flow of the secondary air into the interior of theflame tube 55 from the annular chamber 54 the sheet metal of which theflame tube is formed is deformed or bent around some, preferably all, ofthe distributed apertures 125-129 in the manner shown in Fig. 5 withrespect to one each of the apertures 127, 128 and 129. This deformationis accomplished by suitably formed dies which shape the metal so thatthe openings face toward the oncoming helically advancing air and, ineffect, scoop the air so that it flows tangentially into the internalcombustion chamber. The deformation or bending of the flame tube 55 mayalso be accomplished by inserting a tapered metal bar into the openingsone at a time and, with the bar wedged in the opening mov ing orswinging the bar in a plane transverse to the axis of the tube and in adirection reverse to the flow direction that the helically advancing airmoves in the annular chamber. For example, a tapered bar inserted in oneof the openings 127, 128 or 129, Fig. 5, would be rotatedcounter-clockwise in the plane of the drawing to produce the scoopformations illustrated.

To augment the spiral motion of the advancing air column as it isreleased from discharge end 131 of the innerflame tube 55 the latter isformed with a number of inwardly bent tabs or deflector vanes 132. Thesevanes may be made by cutting a number of relatively shortcircumfere'ntially spaced axial slits in the end of the tube 55 andbending inwardly corresponding ends of the tabs so formed along diagonallines 133. The swirl imparting vanes 132 not only augment the helicalmotion of the advancing air column, but by deflecting outer peripheralportions of the advancing air column to flow diagonally across thecolumn the turbulence of the flame in and beyond the discharge end ofthe flame tube is enhanced with resultant improvement in combustionefliciency. In the case of relatively high viscosity fuels thecombustion is'initiated in the perforated flange tube 55 and continuesas the spirally advancing column of air flame combustion products andfuel and suspension moves forward through thatportion of the outercombustion tube 25 which extends beyond the discharge end 131 of theinner combus- "tion or flame tube 55. The outer combustion tube may, ifdesired, extend beyond the discharge end of-the inner combustion tube adistance equivalent to several times the length of the latter. Such anarrangement results in a heater of awkward and impractical length. Foroperation with fuels over the viscosity range represented by gasoline,jet engine fuel and No. 1 fuel oil, it is satisfactory if theoutercombustion tube 25 be no more than about twice the length of the innerflame tube 55.

Upon being discharged from the outlet end of the outer combustion tube25 the flame and hot gases received in the header 16 are deflected bythe partition '42 into the'lower part of the header chamber 32 wherethey enter the lower group of exchanger tubes 35. From these lowerexchanger tubes the hot gasesand flame, if

;any, are released into the chamber 22 of the headerlS,

flowing upwardly in such header and thence into and through the uppergroup of the exchanger tubes 35. From the latter tubes the products ofcombustion are discharged into the :upper portion of the header 16 andflow thence out the discharge 34. The circulation of air upwardlythrough the heat exchanger chamber between andaround the tubes-35 andthe outer combustion tube 25 heat such air so that it is dischargedthrough the screen 6 at an elevated temperature to provide the desiredspace heating.

The liquid fuel for the burner is received through a main supply conduit135, a conventional motor driven pump 136 drawing the fuel from thesupply line 135 and forcing it under pressure into a conduit 137 whichis connected to the fuel inlet conduit 86 through adjustable pressurereducing valve 138 and a solenoid operated or other electric valve 140,a conduit 139 connecting the reducing valve 138 to the electric valve140.

The electrical power forenergizing the several electrical components ofthe space heater is supplied to the de leads141,142'so that the supplyof fuel to the burner is initiated" by the pump in response to the heatdemand transmitted through the thermally responsive control.

Alternatively the pump 136 can be continuously operated with a suitableby-pass which functions when the electrical valve 140 is closed. In lieuof the pump 136 the fuel may be contained in an elevated tankwithgravity feed into' the fuel system.

Sothat the air mass within the combustion tube structure is properlyconditioned to receive a fuel spray without objectionable deposit ofliquid fuel on the walls of the tube structure and without excessivesmoking on starting, provision is made for establishing spiral air flowin the combustion tube structure before the fuel spray is released.'This is accomplished by a delayed action in the opening of the solenoidvalve 140. The electrical "valve '140 is of the type which is normallybiased to closed position by a spring loaded valvebody and 1S opene'clby electromagnetic action of a solenoid coil or 1 the" like when suchcoil is energized. The electrical enei'gy forthe valve 140 is obtainedfrom the power leads "141, 142 through an interposed pressure responsiveswitch 143' 'vei'nedb'y" the pressure ofthe'airin the secondary difiiitbetweenthe blower120and the annular chamber e 154. The pressure switch143 may, for example, -be

connected by a tube 149 to the flexible hose 148 which joins the blowertakeoff 124 and the inlet tube59 that feeds the secondary air into theannular chamber 54 of the combustion tube structure.

In operation in response to a demand for heat which causes the controlunit to energize electrical power leads 141, 142, the spark ignitionelectrodes 108, 109 are immediately energized through the transformer116 toproduce-aspark infront of the nozzle structure 63. The pump 136 isenergized simultaneously with the transformer-116 to feed the fuel intothe conduit system leading into the nozzle assembly 63. However, theelectric valve 140 being closed prevents the fiow offluid through thenozzle system, since the electrical circuit through the solenoid coil ofthe valve 140 remains de-energized While the pressure switch is in itsnormally openedcondition. The electrical motor 52 driving the blower 120is energized as through the power leads 141, 142 simultaneously with theenergization of the spark ignition transformer'116 and starts the flowofair through the primary supply tubes 147 and 90 and through thesecondary air supply tubes 148 and 59. When the pressure in thesecondary tube 143 is built up to a predetermined minimum whichcorresponds to the normal operating condition so that the air masswithin the combustion tube structure is rotating helically, the pressureswitch 143 responding to the pressure in the tube 148, is actuated toclose the electrical contacts to complete the circuit through thesolenoid coil of the electrical valve 140.

Upon such energization of the electrical valve the fuel supply line isopened and the fuel is projected from the orifice 76 of the nozzlestructure into the combustion chamber through the circular opening 62 ofthe control plate 60, the combustible mixture being ignited by thecontinuous spark maintained between the electrodes 108, 109. While theseelectrodes are shown to be wholly within the normalizing chamber 66, thespark being carried into the combustion zone by the fuel and primary airspray, it is apparent that they may be extended into or through theopening 62. Besides conventional gasoline, plain or leaded, and the No.1 fuel oil of 132,000

B. t. u. per gal, the present burner operates on JP-4 jet fuel. It burnsfuel at a rate as low as about .65 gal per hour delivering about 75,000B. t. u. per hour and is capable of instant starting at temperatures aslow-as F.

In operation the blower 120 delivers air which in the primary supplyline into the nozzle chamber 73 is-at a pressure of from about 4 inchesto about 12 inches of water, preferably, in the range of from about 8inches to about 10 inches of water. In the secondary supply line feedingair into the annular air chamber 54a much lower pressure is maintained,pressures as low as about2- inches of water being satisfactory.

On operation with fuel of relatively low viscosity, such, for example,as gasoline, the tendency of the-flame is to burn-close to the nozzlestructure 63 relative to the posichamber into the normalizing chamber66, the flame produced by low viscosity fuel is apparently heldaway from'close proximity to the-nozzle structure 63 and overheating of thelatter is avoided.

' While the combustion tube structure of the present-invention comprisesa number of components, being the :inner and outer tubes 55 and 25, thesupplemental. tube that a unitary outer tube maybe employed. "case thenozzle structure63 is supported in the centerof "the end closure forsuch unitary outer tube and the controliblatebfl takes'the form of a.partition spacedxaxially from such end closure, the flame tube 55 beingthen a 5 6 and the tubular mounting member 65, it is apparent In such 13separate tube located wholly on the combustion chamber side of thepartition and suitably supported and centered in the unitary outer tube.

In accordance with the patent statutes the principles of the presentinvention may be utilized in various ways, numerous modifications andalterations being contemplated, substitution of parts and changes inconstruction being resorted to as desired, it being understood that theembodiment shown in the drawings and described above and the particularmethod set forth are given merely ing being deformed and bent out of thesurface of revolution and so shaped that air admitted to the interiorthrough such opening moves with a tangential component, means closingone end of the tube whereby air admitted through the openings advancesto and is discharged from the other end of the tube, said advancing airmoving helically under the influence of the tangential components, theother end of the tube being axially slotted at circumferentially spacedpoints, corresponding portions of the metal of the tube adjacent the endslots being bent inwardly and disposed in angular relationship to thelongitudinal axis of the tube in the provision of a plurality ofintegral air deflecting vanes symmetrically spaced about the tube axisat such other end of the tube to intercept and deflect radially inwardlyair being discharged through such other end of the tube and to directsuch intercepted air to flow tangentially relative to the tube inaugmentation of the circumferential component of the helical flowproduced by the deformed metal liquid fuel to the nozzle under pressure.

2. A liquid fuel burner comprising an elongated metal combustion tube inthe form of a surface of revolution and having a multiplicity of axiallyand circumferentially spaced openings for admitting air to the tubeinterior, 1

that portion of the metal of the tube surrounding each opening beingdeformed and bent out of the surface of revolution and so shaped thatair admitted to the interior through such opening moves with atangential component, means closing one end of the tube whereby airadmitted through the openings advances to and is discharged from theother end of the tube, said advancing air moving helically under theinfluence of the tangential components, the other end of the tube beingaxially slotted at circumferentially spaced points, correspondingportions of the metal of the tube adjacent the end slots being bentinwardly and disposed in angular relationship to the longitudinal axisof the tube in the provision of a plurality of integral air deflectingvanes symmetrically spaced about the tube axis at such other end of thetube to intercept and deflect radially inwardly air being dischargedthrough such other end of the tube and to direct such intercepted air toflow tangentially relative to the tube in augmentation of thecircumferential component of the helical flow produced by the deformedmetal openings, a nozzle supported and adapted to project a spray ofliquid fuel into the tube at said one end, a shroud of circular sectionsurrounding the combustion tube in spaced relation in the provision ofan annular air supply chamber, an air delivery tube disposed to releaseair tangentially into the annular chamber,'means supplying air underpressure to the delivery tube whereby air released into the annularchamber first advances helically therein, is then admitted to theinterior of the combustion tube through the openings in the latter, andthen moves helically to the'discliarge end of the tube, and meanssupplying liquid fuel to the nozzle under pressure.

3. A liquid fuel burner comprising an elongated metal combustion tube inthe form of a surface of revolution and having a multiplicity of axiallyand circumferentially spaced openings for admitting air to the tubeinterior, that portion of the metal of the tube surrounding each openingbeing deformed and bent out of the surface of revolution and so shapedthat air admitted to the interior through such opening moves with atangential component, means closing one end of the tube whereby airadmitted through the openings advances to and is discharged from theother end of the tube, said advancing air moving helically under theinfluence of the tangential components, the other end of the tube beingaxially slotted at circumferentially spaced points, correspondingportions of the metal of the tube adjacent the end slots being bentinwardly and disposed in angular relationship to the longitudinal axisof the tube in the provision of a plurality of integral air deflectingvanes symmetrically spaced about the tube axis at such other end of thetube to intercept and deflect radially inwardly air being dischargedthrough such other end of the tube and to direct such intercepted air toflow tangentially relative to the tube in augmentation of thecircumferential component of the helical flow produced by the deformedmetal openings, a nozzle supported and adapted to project a spray ofliquid fuel into the tube at said one end, a tubular shroud of greateraxial length than the combustion tube surrounding the latter in spacedrelation in the provision of an annular air supply chamber, the shroudprojecting axially beyond said other end of the combustion tube anddefining an expansion chamber for receiving flame and hot gasesdischarged from the combustion tube, means supplying air to the annularchamber under pressure to force such air into the combustion tubethrough the tangential component openings, and means supplying liquidfuel to the nozzle under pressure.

4. A liquid fuel burner comprising an elongated metal combustion tube inthe form of a surface of revolution and having a multiplicity of axiallyand circumferentially spaced openings for admitting air to the tubeinterior, means closing one end of the tube whereby air admitted throughthe openings advances to and is discharged from the other end of thetube, a nozzle supported and adapted to project a spray of liquid fuelinto the tube at said one end, a tubular shroud of greater axial lengththan the combustion tube surrounding the latter in spaced relation inthe provision of an annular air supply chamber, the shroud projectingaxially beyond said other end of the combustion tube and defining anexpansion chamber for receiving flame and hot gases discharged from thecombustion tube, an air delivery tube disposed to release airtangentially into the annular chamber adjacent said one end of thecombustion tube, said delivery tube constituting the sole meanssupplying air to the annular chamber, means supplying air under pressureto the delivery tube whereby air released into the annular chamber firstadvances helically therein is then admitted to the interior of thecombustion tube through the openings in the latter, and then moveshelically to the discharge end of the tube, the other end of thecombustion tube being axially slotted at circumferentially spacedpoints, corresponding portions of the metal of the combustion tubeadjacent the end slot being bent inwardly and disposed in angularrelationship to the longitudinal axis of the combustion tube in theprovision of a plurality of integral air deflecting vanes radiallyinwardly air being discharged through such other end of the combustiontube and to direct such intercepted air-to flow helically in the shroudwhereby the air deflecting vanes augment the circumferential componentof the spirally moving air and means supplying liquid fuel to the nozzleunder pressure.

5. In a liquid fuel burner of the type in which a spray comprising amixture of liquid fuel and primary air is projected into a combustionchamber and there commingled with secondary air, the combination of anozzle structure comprising a metal mounting block, a metal body andcooperating metal parts formed with a discharge orifice andseparatepassages extending from the mounting block for conducting fueland air to such discharge orifice, mounting plate means of metal, theplate means having an opening and the nozzle structure being receivedthrough such opening and supported by the mounting plate means in heatconducting relation, the mounting block being generally on one side ofthe mounting plate means and the metal body being generally on the otherside of the mounting plate means, the plate 1means being formed with anannular chamber surrounding the nozzle structure, a cup shaped metalcap, the cap being disposed over the nozzle body and supported by themounting plate means in heat conducting relation, the cap having anopening in alignment with the discharge orifice of the nozzle structure,the cap and the nozzle body :being formed to provide an air circulatingchamber therebetween, means defining another air passage from said firstmentioned air passage in the nozzle structure to the annular chamber,duct means for the flow .of air radially from the annular chamber intothe air circulating chamber between thenozzle structure and the cap,vthe air circulating chamber being continuous with the cap opening sothat air flowing into such air chamber .is discharged through the capopening to commingle with the projected fuel and primary air mixture,the nozzle structure being adapted to project the spray in an expanding.pattern through the cap opening for burning in spaced relationto thecap and the nozzle structure, whereby radiant heat energy directedtoward the nozzle structure from the burning spray is intercepted by the.cap in the elimination of excessive heating of the nozzle structure.

.6. A heater comprising in combination a hollow casing havingside, end,top and bottom panels,'a heat exchanger in the casing, the heatexchanger having spaced h'ollow headers and tubes connected between theheaders for the circulation of hot gases through, the tubes and theheaders, a flue outlet tube extending from one of the headers throughone of the'panelsof the casing, partitions means secured-to the toppanel of the casing in de- -tachablerelation and including spacedparallel side elements and a bottom element connecting. the sideelements, the side elements of 'the partition being spaced-from andparallel torcorresponding-side panels of the casing, the bottonr element:being spaced above the bottom panel of the casing,said partition meansdefining an :open ended 1: vpocket to receive the heat exchanger forfacile removal "and replacemenhthe pocket open end being substantiallyclosed by one of said headers, the partition means and said one'headerdividing the interior of the easing into a heat exchanger chamber and-ablower chamber, one of --"the casing panels being formed with an outletopening communicating directly with the heatexchanger chamber, thecasing being formed with an inlet opening communicating directly withthe blower chamber, a blower secured *to the partition means and solelysupported thereby in suspended relation within the casing, the heatexchanger -being removable from andreplaceable into the pocket in-:dependently of the blower, a motor within the casing and drivinglyconnected to the blower, the blower having -aninletopening within theblower chamber to receive air ;-from;' such chamber and having anoutletopening into atheheat exchanger: chamber: so that: actuation. :of theblower draws air into the blower chamber through said 16 inletopeningrinthe casing and forceslair. into thez heat exchanger chamber and out ofthe casing through said outletopening, a burner assemblycomprising .acombustion tube'having anend for receiving fuel and air and anotherendfor discharging hots products of combustion, a mountingmember securedacross said oneend :ofzthe combustion tube,.a nozzle carried by:themounting memher, the combustion tube extending through said one headeracross the heat exchanger chamber and-having connection at its other endwith the other header todischarge hot gases into the latter, the onereceiving end of air and burn in suspension, the combination'of a fuelnozzle, means defining a combustion chamber, means mounting the; nozzleto direct a fuel spray into the chamber, and ignition means for ignitingthe fuel; the mountl ing means including plate means formed with acentral apertureto receive the nozzle and with an annular chambersurrounding the receivednozzle, the plate means includingone wallelement interposed betweenithe combustion chamberand the annular chamberand another wall element spaced-from theone wall element byirthe annularchamber, the one wall element of the plate means being formedtwith anopening accommodating the electrode, said opening constituting adischarge orifice through which air from the annular chamber :isdischarged into the combustion chamber, the ignitionmeans including anelectrode supported by said other wall element of the platemeans andprojecting therethrough and also projecting through the chamber in theplate means and in insulated relation through the orifice opening :inthe one wall element, said orifice opening being; sufficiently large toprovide clearance space surrounding: the electrode andseparating it fromthe one wall, and means supplying air under pressure to the annularchamber in itherplate means-continuously during operation OfLthG burnerfor circulation of the supplied air through-such .annular chamber aboutthe nozzle and release:through the clearance space of the orificeopening.

8. In a liquid fuel burner of the type in which a spray comprising amixture of liquid fuel and primary .air is projected into a combustionchamber; a nozzle structure fice and separate fuel and air passagesextending from. and

continuous with the corresponding passages of the mounting block forconducting pressurized fuel and air'tov-such discharge orifice; mountingplate means of metal,.1the

. ,plate means having an opening and the nozzle structure beingreceivedzthrough such opening, the plate. means being formed with anannular chamber surrounding the nozzle structure, a cup shaped metalcap, the. cap being disposed over the nozzle body and supported bywthemounting plate means, the cap having. anqopeninghin alignmentwith thedischarge orifice of the nozzle structure, the cap and the nozzle bodybeingv formed to provide an air circulating chamber therebetween, meansdefining another air passage from said first mentioned1air passagexinthe nozzlerstructure to the annular chamber, rneans providing a passagefor the flow of air radially from the annular chamber into the aircirculating chamber between thenozzle structure and the cap, the aircirculating chamber being continuous with the capopening .so' thatrairflowing, intosuch air chamber is discharged through rthe cap openingto-commingle with the projected ,fueliand primarytair; mixture, thenozzle structureabeing adapted to project the spray in an expandingpattern 17 through the cap opening for burning in spaced relation to thecap and the nozzle structure, whereby radiant heat energy directedtoward the nozzle structure from the burning spray is intercepted by thecap in the elimination of excessive heating of the nozzle structure.

References Cited in the file of this patent UNITED STATES PATENTS 18Arnold Oct. 10, 1939 McCollum Dec. 4, 1945 Holthouse Jan. 15, 1946 Meyeret a1 June 17, 1947 Arnhym July 20, 1948 Logan et al July 18, 1950Caracristi Dec. 23, 1952 Schumann Mar. 16, 1954 FOREIGN PATENTS FranceNov. 1, 1950 Germany Nov. 15, 1913 Great Britain June 13, 1951

